Marcus Coco struck twice as Guingamp came from behind to stun Lyon 3-1 at the Parc Olympique Lyonnais on Saturday.
Les Gones took the lead through Alexandre Lacazette's penalty eight minutes before half-time, after visiting midfielder Moustapha Diallo had tripped Maxime Gonalons.
But Guingamp were back on level terms within moments of the restart. Jimmy Briand won possession in the Lyon half and his attempted cut-back fell to Yannis Salibur, who fired past Anthony Lopes.
The visitors took the lead in the 52nd minute when Lyon's sloppiness on the ball again proved costly, this time Briand setting up Coco to tap in.
The 20-year-old midfielder sealed matters by grabbing his second goal of the match 15 minutes later, blasting beyond Lopes after skipping past home full-back Rafael.